Tunnel drilling apparatus with drill waste removal

ABSTRACT

A drill head for drilling a tunnel in rock or soil comprises a rotatable drill bit assembly and a cylindrical protecting tube. The bit assembly comprises a bit holder and a cylindrical drill bit. The bit assembly has a cylindrical surface which forms a continuous cylindrical lap joint with the protecting tube. The bit assembly also has at least one opening for removing, through the bit assembly, drill cuttings from the face of the drill bit. In use, the lap joint allows rotation of the drill bit assembly relative to the protecting tube and prevents access of the drill cuttings to the outside of the drill head.

The invention relates to a tunnel drilling apparatus provided with aworking tool at drill head and to a method by means of which the drillwaste is removed from the working tool inside the protecting pipe.

Previously is known tunnel drilling apparatus with one working tool a.o.from the U.S. Pat. No. 4,122,683. A working drill head that rotates oncutting the tunnel front wall is introduced in the publication. Theexcavated material is shifted into the protecting tube of the drill headand further to the rear end of the apparatus. The apparatus has aplurality of abutments immobilized against the tunnel walls enablingadjustment of the drilling direciton by providing support from thetunnel walls to the protecting tube and turning the tool or the mobilepart of the tool head in desired direction for instance by means ofturning cylinders.

The U.S. Pat. No. 2,919,121 introduces an apparatus with one tunneldrilling tool by means of which excavated material is shifted into arotating tube. Outside this tube there is another tube, the actualprotecting tube enveloping the drill head. This tube is supported bywheels and expanding ring segments against the tunnel walls andadjustment of the drilling direction is provided with these wheels andring segments.

The disadvantage of the above described solutions is characterized inthat the excavated material has access to the bottom of the tunnelduring working because of the placement of bit components in appliedtools with respect to the protecting tube. A space is left open betweenthe bits and the protecting tube, where excavated material simply pilesup. It is complicated to force the material between the protecting tubeand the driving tube and even not quite possible in driving a tunnel inunbroken rock. In these cases, a certain quantity of drill waste alwaysremains in the tunnel, which means hindrance to the drill headalignment, since control of driving is effected through leaning on thetunnel walls. Then disturbing drill waste piles up especially in thelower parts of the tunnel and wedges itself between the protecting tubeand the tunnel.

The method and apparatus according to this invention provide a crucialimprovment of said disadvantages. In order to put this into practice,the method and apparatus are characterized in what has been described inthe enclosed patent claims.

It can be considered the main advantage of the invention that the drillhead can force itself through to the inner surface of the reliablywaste-free tunnel which makes it possible to use a simple directforward-driving drill head without any kind of control equipment.Furthermore, a lap joint prevents access of loose soil from tunnel uppersurface to striking bit neck portion, where it would cause interruptionof drill bit stroke in no time at all. Advantageously, the method ofthis invention is applicable to tunnels with small-sized diameters,preferably to ones with diameters under 800 mm. In addition, theadvantage of this invention is increased since it is especiallydifficult to furnish small-diameter drill heads with control equipment.

In the following the invention is described in detail with reference tothe enclosed drawing.

FIG. 1 is a drill head with a tool.

FIG. 2 is a drilling apparatus resting on the tunnel bottom firmlysupported by the steering tunnel walls.

The tool (4) in FIG. 1 comprises a bore bit holder (51) with openings(2), along which the drill waste is conveyed by compressed air from thefront end of bit 1 to the protecting tubes (3,7). Compressed air entersthe tool along a hose (8) and at least a part of it is conducted to thebit front end to convey drill waste. Between the drill bit holder andits protecting tube (3), there is a lap joint to prevent access of drillwaste to the outside of the protecting tube. Arrangement of position anddirection of openings (2) makes it possible to provide an ejector effectin the lap joint so that even drill waste, which may have somehow passedthe drill bit, is sucked up into the protecting tube. The collar ring(52) provided with openings is attached to the protecting tube but is,on the other hand, also in a groove of the tool, thus securing the lapjoint when the bit component is moving in operation.

The protecting tube comprises two parts, one of them (7) attached to theother by screws (6). The tool is supported with rolls (5, 17) againstthe protecting tubes. The hydraulic cylinder (10), the piston (11) andthe piston rod (9) function as a thrust bearing. The rotating conveyordrum (15) has ribbings (14) that convey the waste away from the drillhead. The line of compressed air and the hydraulic hoses (19, 20) to thedrill head are arranged in the back of this ribbing. Compressed air isconducted from the rotating tube by means of a collector ring (12) to animmobile pipe. The collector ring is secured to the protecting tube withbraces (18).

The tool (25) in FIG. 2 is provided with a drill bit (21) and a bitholder (51). Compressed air is conducted also to the bit front end andfurther through the bit and its openings (22) into the pretecting tubes(23, 28) to convey waste as it advances. The tool head is secured with abearing support (24). In the protecting tubes holdfast points againsttunnel bottom adjusting rings (26,36) are fitted with screws (notshown). Adjustming rings of different height or only sliding brackets(38) can be used on protecting tubes lower surface. The interterpositionof the protecting tubes can be adjusted with turning cylinders (46)secured with brackets (45) to the protecting tubes. The rotating motionis brought to the tool by means of a conveying drum (39) provided withan internal ribbing (40) and a compressed air line (42) and hydraulichoses (41) are arranged behind it. To the front edge of the conveyingdrum (39) a cylindrical part (37) is fastened with brackets (38), thefront face of which functions as a thrust bearing area and the shellsurface as a radial bearing area. From this part the rotation istransmitted to the tool by means of a bushing (30). The inner bushing(43) is also rotating and from its inside the drill waste is shifted tothe conveying drum. Around the bushing (30) an immobile hydraulicpressure distributor (33) is blocked into position by means of a collarring (32). The roller system (34) functions as a thrust bearing and therollers (35) as a radial bearing.

This invention is not restricted to the embodiments of prior art but itcan be modified within the limits of the enclosed patent claims.

I claim:
 1. A drill head comprising a rotatable bit assembly and acylindrical protecting tube, said bit assembly comprising a bit holderand a cylindrical drill bit, said bit assembly having a cylindricalsurface for forming a continuous cylindrical lap joint with saidprotecting tube, said lap joint allowing relative longitudinal movementof said bit assembly and said protecting tube, and having at least oneopening for removal, through the bit assembly, of drill cuttings fromthe face of the drill bit, said cylindrical protecting tube forming withsaid cylindrical surface of said drill bit assembly a continuouscylindrical lap joint between said bit assembly and said protectingtube, said lap joint, in use of the drill head, allowing rotation ofsaid drill bit assembly relative to said protecting tube and preventingaccess of said drill cuttings to the outside of said drill head.
 2. Adrill head according to claim 1 wherein said cylindrical drill bitcomprises a percussing bit.
 3. A drill head according to claim 1 furthercomprising means for forcing said drill cuttings through said at leastone opening in said bit assembly.
 4. A drill head according to claim 1wherein said lap joint is at least as long as the distance of saidrelative longitudinal movement.
 5. A drill head according to claim 1further comprising means for limiting said relative longitudinalmovement.
 6. A drill head according to claim 5 wherein said movementlimiting means comprises a cylindrical collar fixed to the inner surfaceof said protecting tube.
 7. A drill head according to claim 6 whereinsaid movement limiting means further comprises a cylindrical groove insaid bit assembly, said cylindrical collar being longitudinally moveablein said groove and being engageable with the walls of said groove.
 8. Adrill head according to claim 1 wherein said cylindrical surface isprovided on said bit holder.